[Bf-cycles] GSoC - Spectral Rendering

Ton Roosendaal ton at blender.org
Wed Apr 10 16:58:14 CEST 2013


I agree with Agus here.

Cycles is meant to be a production render engine, to work well for renders of animation sequences, where render time is a very relevant issue.

Our experience with Tears of Steel renders were quite mixed for it, there's a lot of work we could do to investigate better sampling, noise reduction, or related features that give speedup.

Plenty of interesting papers exist in this area, like:

Important topics for cycles is still volumes, GPU hair, baking, shader editing, FSA etc. All stuff that would help people using it for animation or vfx renders.


Ton Roosendaal  Blender Foundation   ton at blender.org    www.blender.org
Blender Institute   Entrepotdok 57A  1018AD Amsterdam   The Netherlands

On 10 Apr, 2013, at 3:36, Agustin Benavidez wrote:

> Hi, my humble opinion is that this idea somehow doesn't fit into the Cycles philosophy and focus which is be the best balance between speed and realism/accuracy and animation oriented, We already got great render engines capable of that integrated in blender like Luxrender, spending a Summer Of Code slot to re-do what others complementary OOS projects do best is not worth.
> Here is what you can already do with a relative simple node setup:
> http://www.youtube.com/watch?v=jMsW5gPqS6c
> http://www.blendswap.com/blends/view/39307
> I understand dispersion is not only about little rainbows, but I agree with Dalai, and don't see this improving Cycles general usage. 
> Anyway We need to be open and will be nice to see some examples of the quality boost that this could bring :)
> Best regards.
> Agus
> 2013/4/9 Gavin Howard <gavin.d.howard at gmail.com>
>      David,
>      Cycles has a subsurface scatter node in the development builds,
> correct? If that's the case, I will see if I can render some scenes in
> Cycles and LuxRender to show the difference. It's not going to be the
> best, but it should show something.
>      Gavin H.
> On Tue, Apr 9, 2013 at 5:20 PM, David <erwin94 at gmx.net> wrote:
> > On Apr 10, 2013, at 12:55 AM, Brecht Van Lommel wrote:
> >> On Wed, Apr 10, 2013 at 12:08 AM, David <erwin94 at gmx.net> wrote:
> >>> this is by far the best visual explanation of what separates spectral
> >>> rendering from normal RGB rendering that I have seen:
> >>>
> >>> http://www.luxrender.net/wiki/LuxRender_Textures_Spectrum#Gaussian_spectrum
> >>>
> >>> All lamps in this image would be the same RGB color, and produce the
> >>> same result with non-spectral rendering.
> >>
> >> I don't think that's true? The exact result depends on the wavelength
> >> to RGB conversion function, but a wider gaussian distribution across
> >> the wavelength should give different RGB values than a narrow one? As
> >> the distribution gets wider there will a more even distribution across
> >> the RGB channels.
> >>
> >> It wouldn't be as accurate but the lights would still render different I think?
> >>
> >> Brecht.
> >
> > Ah, you're right, and it is even sort of explained in the text I linked to, so I
> > feel especially dumb. ;)  The width of the distribution corresponds roughly to
> > saturation, it's basically just HSV.
> > So, the only effect that I can think of that is really not approximated by RGB
> > rendering is dispersion? I would love to see an image where the light spectrum
> > makes a noticeable difference, that isn't of a prism or a diamond...
> >
> > till then, David.
> >
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